Automatic damper for downflow furnaces



y 20, 1953 J. A. BARRY 2,835,339

AUTOMATIC DAMPER FOR DOWNFLOW FURNACES Filed Dec. 12, 1955 a m .m MR TA g NB n W .r. NR E B L u A. N 7 AHUH 2 B ATTORNEY 5 2,835,339 Patented May 20, 1958 AUTOMATIC DAMPER FOR DOWNFLOW FURNACES John Albert Barry, Salem, reg.; Alfrieda Frances Barry,

admlmstratnx of said John Albert Barry, deceased, asslgnor to Vern Reiman, Salem, Oreg.

Application December 12, 1955, Serial No. 552,433 1 Claim. (Cl. 183-32) This invention relates to automatic dampers for downflow furnaces.

There are many advantages in downflow furnaces in heating, but they also have some disadvantages at the present time. One of these disadvantages is that lint or other inflammable material gathers in the return air duct leading from the heated area, which creates an undesirable, dangerous condition in the return air duct.

Another objection has been that when the blower or fan is not operating, the residual heat from the heat exchanger within the furnaces flows up through the blower or fan, which is usually mounted just above the heat exchanger, and into the return duct. This residual heat damages the drive motor of the fan, together with its bearings and other movable parts. Therefore, it is the primary object of this invention to overcome this disadvantage in downflow furnaces.

In the carrying out of this object, an automatic damper is disposed or located between the air blower and the heat exchanger chamber. This damper remains closed until the heat within the heat chamber of the furnace has risen to a predetermined amount when the limit switch starts the blower motor, at which time the damper is automatically opened. When the blower is stopped due to the heated area reaching the pre-set temperature, this damper automatically closes preventing residual heat from passing up through the blower and into the return air ducts, thereby protecting the blower motor and preventing it from becoming overheated.

Other objects and advantages will become apparent in the following specification when considered in the light of the attached drawings, in which:

Figure 1 is a side elevation of the invention shown installed in a downflow furnace, partly in section;

Figure 2 is a horizontal section, taken on line 2-2 of Figure 1, looking in the direction of the arrows;

Figure 3 is a side elevation of the damper unit, partially broken away;

Figure 4 is an enlarged fragmentary horizontal section, taken on line 44 of Figure 3, looking in the direction of the arrows;

Figure 5 is a wiring diagram of the electrical controls for controlling the blower and the automatic damper, including the limit switch, and

Figure 6 is a view similar to Figure 3 of a modified form of damper control wherein the flow of air opens or closes the damper.

Referring now to the drawings in detail, wherein like reference numerals indicate like parts throughout the several figures, the furnace is indicated generally by the letter F, while the heat exchanger is indicated generally by the letter H and the blower generally by the letter B. The usual structure of the furnace F of this sort is that the blower B is superimposed above the heat exchanger H, its discharge nozzle 10 passing through a diaphragm 11 forming part of the furnace F. The blower B draws air down through the air duct 12, through the blower B and into a heat exchanger chamber 13.

With this invention the nozzle 10 of the blower B directs air through an automatic damper, generally indicated at D, and into the chamber 13. The damper D consists of a rectangular shell 14, having side walls 15 connected by end walls 16 and having neither top nor bottom closures. Disposed within the shell 14 are rotatable damper blades 17. These blades 17 are positioned within the shell 14 by the spindles 18 which pass through openings within the end walls 16 of the shell 14 of the damper D. Cranks 19 are fixedly secured to the spindles 18 on one end of the damper blades 17 and are connected together by the link 20.

An electric solenoid 21 is fixedly secured to the side wall 22 of the furnace at 23. The core 24 of the solenoid 21 is connected to the end of the link 20 of the levers 19 by way of the reduced extensions 25 and the link 26. A spring 27 is located in the rear end of the core 24 of the solenoid 21 and tends to force the core 24 in the opposite direction of the arrow, shown in Figure 3, holding the damper blades 17 in the closed position shown.

Asbestos or other heat insulating material 28 is applied to the face of the damper blades 17 to prevent heat from radiating therethrough into the blower chamber 29 of the furnace F.

Referring to Figure 6, a modified form of operation of an automatic damper D is illustrated wherein a counterweight 30 is adapted to close the damper blades 17.

The pivot spindles 18 being located towards one edge of the blades 17. In operation the counterweight 30 of this form of damper D closes the damper blades 17, but the instant that the blower B begins to force air therethrough against the blades, these blades will be moved to open position due to the offsetting of the spindles 18, as illustrated in Figure 6. When the air flow stops, the counterweight 30 will close the damper D.

The motor for operating the blower H is indicated by numeral 31, while the usual limit switch 32 for controlling the operation of the motor 31 is positioned in the heat exchanger chamber 13. The usual type of air filter 34 is located between the blower B and the air duct 12, referring to Figure 1.

The operation of the damper D will now be described. When sufficient heat has been developed within the heat chamber 13 by the heat exchanger H, the limit switch 32 will close. This will supply energy to the solenoid 33 of the relay R closing the same. The motor 31 will be energized driving the blower B. Also the solenoid 21 will be energized opening the damper D permitting air to flow therethrough.

The blower B will operate until after the thermostat (not shown) within the room being heated, operates, shutting oif the fuel supply to the heat exchanger H, and the heat drops within the heat exchanger chamber 13, operat ing the limit switch 32 which will open, shutting off the motor 31, and also demagnetizing the solenoid 21 allowing the spring 27 to force the core 24 to the position shown in Figure 3, operating the cranks 19 by the link 20, closing the damper D so that no heat will be allowed to enter through the damper D into the blower chamber 29 of the furnace F or the air duct 12 of the heating systern.

It can be readily understood by the drawings and description that it is the purpose of this invention to close the path of air through the air intake duct and blower when the blower is not in operation, and to open the same when the blower is operated, either mechanically or electrically.

What is claimed is: I

A downflow hot air furnace of the type having a heat exchanger, an air housing surrounding said heat exchanger and extending upwardly substantially thereabove,

3 a horizontal partition positioned in said housing over said heat exchanger, a centrifugal blower mounted in said housing above said partition, said housing having an upwardly extending cold air inlet conduit communicating therewith above said partition and being adapted to communicate with a hot air outlet conduit adjacent the lower end of said housing, and a porous air filter positioned between said cold air inlet and said housing over said blower, a damper attachment comprising a generally rectangular passage-forming shell having spaced vertical side walls connected by spaced vertical end Walls with said side and end walls extending perpendicularly through a rectangular opening in said partition, a plurality of parallel damper blades positioned in said shell for movement from a generally vertical position to an overlapping generally horizontal position, a spindle fixed to each end of each of said blades with the spindles on opposite ends of each blade arranged in axially aligned relation, said spindles having axes lying substantially in the same horizontal plane and the spindles of one blade being parallel to the spindles of the remaining blades, said spindles each extending through and journaled in one of said end walls whereby said blades may pivot from said overlapping generally horizontal position closing the passage formed by said shell to said generally vertical position opening said passage, a crank secured at one end thereof to each spindle adjacent one end of said shell, a link pivotally secured to the opposite ends of each of said cranks, and means controlled by the operation of said blower for pivoting said blades from closed position to open position and for pivoting said blades from open position to closed position when said blower becomes inoperative to prevent warm air flow through said shell over said blower and out said cold air inlet.

References Cited in the file of this patent UNITED STATES PATENTS 

